"At peak workloads, the U.S. Bureau of Customs and Border Protection’s database processes 51,448 transactions per second, nearly twice its peak of 26,655 TPS in 2001. It has the distinction of being the hardest-working transactional database in the world, according to survey results released earlier this month. Experian Marketing Services Inc. has the busiest decision-support database, handling 887 simultaneous queries at its peak workload."
This article notes that MS SQL Server is now often used for the biggest and baddest databases. This happened in just the last four years, and there are probably very few computing tasks left that Windows Server can’t handle. Now that scalability is there and reliability is getting better, Microsoft needs to nail down security to be really credible as an enterprise platform vendor.